The Effect of Temperature on Fatigue Strength and Cumulative Fatigue Damage of FRP Composites

Fatigue 2010 The Effect of Temperature on Fatigue Strength and Cumulative Fatigue Damage of FRP Composites H. Mivehchi, A. Varvani-Farahani* Department of Mechanical & Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario M5B 2K3 Canada Received 28 February 2010; revised 10 March 2010; accepted 15 March 2010 Abstract Polymer-matrix composites are viscoelastic materials and their mechanical properties are significantly influenced by temperature. The present study intends to investigate the effect of temperature on cumulative fatigue damage (D) of laminated fibre-reinforced polymer (FRP) composites. The fatigue strength (S-N relation) of FRP composite laminates was formulated with temperature- dependent parameters. The effect of temperature was further included in the fatigue damage approach formulated earlier by Varvani and Shirazi. The analysis was developed to assess the fatigue damage of FRP composites at various temperatures (T). Inputs of the proposed analysis included temperature-dependent parameters including Young’s modulus (E), ultimate tensile strength ( ult ), and fatigue life (N f ). The proposed temperature-dependent terms and equations were evaluated with the experimental data available in the literature. Temperature dependant-parameters of Young’s modulus, ultimate tensile strength, and S-N relation were found to be responsive when used for unidirectional, cross-ply, and quasi-isotropic FRP laminates. The proposed fatigue damage model was examined using six sets of fatigue damage data and was found promising to predict the fatigue damage of unidirectional (UD) and orthogonal woven FRP composites at different temperatures. Keywords: Temperature; Young’s Modulus; Ultimate Tensile Strength; S-N Relation; Fatigue Damage; FRP Composites. 1. Introduction The major fatigue models and life time methodologies for FRP composites are classified in three categories: (i) fatigue life models, which do not take into account the actual degradation mechanisms, such as matrix cracks and fibre fracture, but use S-N curves or Goodman-type diagrams and introduce some fatigue failure criteria [1-4], (ii) phenomenological models for residual stiffness/strength [1,5-8], and (iii) progressive damage models which analyze the fatigue damage based on some measurable damage variables such as transverse matrix cracks and delamination size [1,9-11]. The fatigue damage model employed in this study is constructed based on stiffness degradation of materials over life cycles. Stiffness degradation damage models [5-7] are reliable approaches relating damage progress of FRP * Corresponding author: Tel.: 01-416-979-5000 Ext. 7707; fax: 01-416-979-5265. E-mail address: [email protected]. c 2010 Published by Elsevier Ltd. Procedia Engineering 2 (2010) 2011–2020 www.elsevier.com/locate/procedia 1877-7058 c 2010 Published by Elsevier Ltd. doi:10.1016/j.proeng.2010.03.216 Open access under CC BY-NC-ND license. Open access under CC BY-NC-ND license. brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Elsevier - Publisher Connector

The Effect of Temperature on Fatigue Strength and Cumulative Fatigue Damage of FRP Composites

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temperature

youngâ s modulus

ultimate tensile strength

sn relation

fatigue damage

frp composites